1. Field of the Invention
The present invention relates to a clutch release bearing assembly for a vehicle powertrain that is manually greased to lubricate a bearing and a bushing.
2. Background Art
Vehicles with manual transmissions generally have a clutch release bearing that is used to engage and disengage a clutch. The clutch is interposed between the engine and transmission on the input shaft of the transmission.
The clutch is engaged and disengaged to selectively transfer torque from the engine to the transmission. The clutch transmits torque to the transmission from the input shaft when the clutch is engaged. The clutch release bearing assembly remains stationary relative to the rotating input shaft and clutch. A release fork is manipulated by either a mechanical or a hydraulic linkage which engages the release bearing assembly. When a clutch pedal is depressed, the release fork is rotated by the linkage to cause the release bearing assembly to move parallel to the input shaft. Depression of the clutch pedal releases the clutch and interrupts the flow of torque to the transmission.
The relative motion between the release bearing and the shaft makes it necessary to provide a bushing and a bearing in the clutch release bearing assembly. The bushing and bearing require lubrication to prevent undue wear of the input shaft, bushing and bearing. Lubrication is provided to both the bearing and the bushing of the release bearing assembly to extend the life of the release bearing assembly. Some release bearing assemblies have grease zerks for lubricating the bearing and the bushing at scheduled maintenance intervals. Conventional clutch release bearing assemblies are designed to allow grease to flow to an unsealed bearing. However, current designs fail to provide a direct path for grease to flow from the grease zerk to the bushing.
Alternatively, some clutch release bearing assemblies may have a sealed bearing and a durable bushing. Sealed bearings and durable bushings reduce the need to lubricate the clutch release bearing assembly but are expensive options. Sealed bearings do not require manual or external lubrication because they are sealed to retain lubricant within the bearing assembly. Sealed bearings tend to interfere with the flow of grease to the bushing which may become starved of lubrication. Sealed bearings minimize problems presented by contamination as a result of their sealed construction but do not generally provide an effective way of preventing contamination from reaching the bushing of the clutch release bearing assembly.
A leaf spring may be included in a clutch release bearing assembly for the purpose of preventing an outer race of the bearing from rotating with the inner race of the bearing that rotates with the same angular velocity as the clutch. The use of such a leaf spring increases the cost of the release bearing assembly.
In current clutch release bearing designs, sufficient lubrication may be provided to the bearing when the bearing is relubricated but the flow path of the lubricant may be obstructed by the outer bearing race. At regular service intervals, grease is applied through the zerk until the grease purges through the cover of the release bearing housing. Grease flow to the bearings is indirect in that it must flow in a serpentine path through the bearing before it reaches the input shaft and bushing. Grease may be initially injected into the clutch release bearing when assembled to provide lubrication to the bushing, however, it is difficult to reliably relubricate the clutch release bearing assembly after the vehicle is put into service.
Prior art release bearing designs that do not use a sealed bearing tend to be more subject to contamination of the bearing. With either a sealed bearing or a non-sealed bearing, contamination is not effectively excluded from the bushing because the bushing is left open to contamination.
There is a need for a clutch release bearing assembly that effectively retains grease and excludes contamination from entering and contaminating the bearing and bushing. As summarized below, Applicants have addressed the above problems and have fulfilled the need for a clutch release bearing assembly that provides adequate lubrication to both the bearing and bushing while excluding contamination from the bearing and bushing.